The famed bird now finds itself at the center of a flap over de-extinction

In the fall of 1813, John James Audubon was traveling by horseback to Louisville from his home in Henderson, Kentucky, when he saw an immense flock of birds coming straight at him. Audubon—pioneer, frontier merchant, peerless bird artist and the creator of The Birds of America— stopped to witness one of the greatest natural spectacles ever seen.

The birds swept overhead from one edge of the sky to the other. “The air was literally filled with Pigeons,” Audubon wrote. “The light of noon-day was obscured as by an eclipse, the dung fell in spots, not unlike melting flakes of snow; and the continued buzz of the wings had a tendency to lull my senses to repose.”

When Audubon reached Louisville at the end of the day, the pigeons were still flying, their ranks undiminished. The banks of the Ohio River in the city were crowded with men and boys shooting at the flock, and dead pigeons were piled at their feet. The flight continued through the night and into the next day—and then the next.

And then they were gone. Only a century after that flock passed through Kentucky like a hurricane, the last passenger pigeon died in a drab cage at the Cincinnati Zoological Gardens. Her name was Martha. Today, she resides, in taxidermied form, at the Smithsonian National Museum of Natural History, where she is on view through October 2015 in the exhibition “Once There Were Billions”—accompanied by specimens of three other extinct avian species: the great auk, Carolina parakeet and heath hen.

Passenger pigeons were handsome birds, half again the size of a mourning dove. Males had gray-blue backs and wings, with a copper-colored breast, while females such as Martha were a duller version of this.

In spring 1860, a flock of passenger pigeons estimated at more than 3.7 billion flew over Ontario. The largest documented nesting of passenger pigeons occurred in Wisconsin in 1871: An estimated 136 million breeding birds covered some 850 square miles of forest. Roosting passenger pigeons often landed in sufficient numbers to shear limbs from trees. But by 1890 passenger pigeons were an unusual sight in the wild—they had become a prized food source, hunted relentlessly, shot, netted and burned out of trees, for a huge commercial market. By 1900 no more than a handful were reported.

The clearing of Eastern forests was another factor in their extinction. Another possible explanation for the rapid demise was that the bird had evolved to live and reproduce in large colonies. When their numbers were reduced, even though there were still many passenger pigeons, breeding success declined. Predation—by humans or natural enemies—had a greater impact.

Martha never lived in the wild. She was probably born into a captive flock at Chicago’s Brookfield Zoo (her mother may have earlier resided in the Milwaukee Zoo). Martha was later donated to the Cincinnati Zoo. In 1900, these three populations were essentially all that was left of a species that may have made up as much as 40 percent of the North American bird population.

Recently, Martha has become the unlikely heroine of a new debate that seems to come out of a science fiction novel. A handful of naturalists and molecular biologists believe that we could one day undo what happened by re-engineering the bird’s genome from preserved specimens and a closely related extant species, the band-tailed pigeon. De-extinction has been proposed as a way of bringing back a number of vanished species, including the woolly mammoth. But it’s the passenger pigeon that is currently getting the most attention.

Some conservationists worry that this approach, ironically enough, could undermine efforts to maintain endangered or threatened species. Where’s the urgency to save a condor if one could simply recreate the species later? Other scientists argue that it will never be possible to restore an extinct species whose habitat has been permanently lost.

Yet many researchers believe that what we might learn from resurrecting a passenger pigeon could ultimately pay big dividends. Jonathan Coddington, the Smithsonian’s associate director of science, is among those who see benefits. “This work is an interesting technical challenge,” Coddington says. “And it’s certain that genetic engineering is going to aid conservation and biodiversity efforts in the coming years.”

Because avian behavior results from a mix of genetics and the imprinting of parental actions, no one knows how a re-engineered passenger pigeon would learn to be a passenger pigeon. Perhaps the birds would be little more than a genetic approximation of their extinct relatives, unable to survive in the wild. “A passenger pigeon in a glass—even if possible—would still be just a passenger pigeon in a glass,” says Coddington.

The “next” passenger pigeon, if there ever is one, might lead a life not so different from that of the last of the original species. In her final days, Martha lived alone. Her wings drooped and she trembled. Keepers had to rope off her cage to prevent visitors from throwing sand to make her move. She died in the early afternoon of September 1, 1914. Her body was packed in ice and shipped to the Smithsonian Institution, where she was skinned and mounted.

According to Smithsonian curator Helen James, Martha represents all that is valuable in nature. “Extinction is not always something that happened in the remote past and in some faraway place,” says James. “The passenger pigeon lived right here, in North America. And in Martha we have something unique: the very last known individual of her kind.”

The exhibition "Once There Were Billions: Vanished Birds of North America," produced by the Smithsonian Libraries, is on view at the National Museum of Natural History through October 2015.

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About William Souder

William Souder is an American journalist who has written for many publications including the New York Times, Washington Post and Slate. Souder is the author of A Plague of Frogs, On a Farther Shore and the 2004 Pulitzer-nominated book Under a Wild Sky about John James Audubon.